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118-407: Valgrind was originally designed to be a freely licensed memory debugging tool for Linux on x86 , but has since evolved to become a generic framework for creating dynamic analysis tools such as checkers and profilers. Valgrind is in essence a virtual machine using just-in-time compilation techniques, including dynamic recompilation . Nothing from the original program ever gets run directly on

236-427: A branch delay slot . Unless the branch delay slot is filled by an instruction performing useful work, an nop is substituted. MIPS I branch instructions compare the contents of a GPR (rs) against zero or another GPR (rt) as signed integers and branch if the specified condition is true. Control is transferred to the address computed by shifting the 16-bit offset left by two bits, sign-extending the 18-bit result, and adding

354-402: A load delay slot . The instruction in the load delay slot cannot use the data loaded by the load instruction. The load delay slot can be filled with an instruction that is not dependent on the load; a nop is substituted if such an instruction cannot be found. MIPS I has instructions to perform addition and subtraction. These instructions source their operands from two GPRs (rs and rt), and write

472-428: A negative or positive liberty . Due to their restrictions on distribution, not everyone considers copyleft licenses to be free. Conversely, a permissive license may provide an incentive to create non-free software by reducing the cost of developing restricted software. Since this is incompatible with the spirit of software freedom, many people consider permissive licenses to be less free than copyleft licenses. There

590-500: A 32-bit and a 64-bit architecture: MIPS32 and MIPS64. Both were introduced in 1999. MIPS32 is based on MIPS II with some additional features from MIPS III, MIPS IV, and MIPS V; MIPS64 is based on MIPS V. NEC , Toshiba and SiByte (later acquired by Broadcom ) each obtained licenses for MIPS64 as soon as it was announced. Philips , LSI Logic , IDT , Raza Microelectronics, Inc. , Cavium , Loongson Technology and Ingenic Semiconductor have since joined them. MIPS32/MIPS64 Release 5

708-465: A 6-bit opcode. In addition to the opcode, R-type instructions specify three registers, a shift amount field, and a function field; I-type instructions specify two registers and a 16-bit immediate value; J-type instructions follow the opcode with a 26-bit jump target. The following are the three formats used for the core instruction set: MIPS I has instructions that load and store 8-bit bytes, 16-bit halfwords, and 32-bit words. Only one addressing mode

826-476: A computer program entails that the source code —the preferred format for making changes—be made available to users of that program. While this is often called "access to source code" or "public availability", the Free Software Foundation (FSF) recommends against thinking in those terms, because it might give the impression that users have an obligation (as opposed to a right) to give non-users

944-529: A copy of the free application itself. Fees are usually charged for distribution on compact discs and bootable USB drives, or for services of installing or maintaining the operation of free software. Development of large, commercially used free software is often funded by a combination of user donations, crowdfunding , corporate contributions, and tax money. The SELinux project at the United States National Security Agency

1062-592: A copy of the program. Although the term "free software" had already been used loosely in the past and other permissive software like the Berkeley Software Distribution released in 1978 existed, Richard Stallman is credited with tying it to the sense under discussion and starting the free software movement in 1983, when he launched the GNU Project : a collaborative effort to create a freedom-respecting operating system , and to revive

1180-552: A corresponding microMIPS32/64 version. A processor may implement microMIPS32/64 or both microMIPS32/64 and its corresponding MIPS32/64 subset. Starting with MIPS32/64 Release 6, support for MIPS16e ended, and microMIPS is the only form of code compression in MIPS. The base MIPS32 and MIPS64 architectures can be supplemented with a number of optional architectural extensions, which are collectively referred to as application-specific extensions (ASEs). These ASEs provide features that improve

1298-428: A drop in revenue to the proprietary software industry by about $ 60 billion per year. Eric S. Raymond argued that the term free software is too ambiguous and intimidating for the business community. Raymond promoted the term open-source software as a friendlier alternative for the business and corporate world. MIPS architecture#MIPS32 MIPS ( Microprocessor without Interlocked Pipelined Stages )

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1416-561: A fee. The Free Software Foundation encourages selling free software. As the Foundation has written, "distributing free software is an opportunity to raise funds for development. Don't waste it!". For example, the FSF's own recommended license (the GNU GPL ) states that "[you] may charge any price or no price for each copy that you convey, and you may offer support or warranty protection for

1534-450: A fee." Microsoft CEO Steve Ballmer stated in 2001 that "open source is not available to commercial companies. The way the license is written, if you use any open-source software, you have to make the rest of your software open source." This misunderstanding is based on a requirement of copyleft licenses (like the GPL) that if one distributes modified versions of software, they must release

1652-489: A lack of source code, there can exist additional obstacles keeping users from exercising freedom over a piece of software, such as software patents and digital rights management (more specifically, tivoization ). Free software can be a for-profit, commercial activity or not. Some free software is developed by volunteer computer programmers while other is developed by corporations; or even by both. Although both definitions refer to almost equivalent corpora of programs,

1770-466: A new data type, the Paired Single (PS), which consisted of two single-precision (32-bit) floating-point numbers stored in the existing 64-bit floating-point registers. Variants of existing floating-point instructions for arithmetic, compare and conditional move were added to operate on this data type in a SIMD fashion. New instructions were added for loading, rearranging and converting PS data. It

1888-415: A pair of 32-bit registers called HI and LO, since they may execute separately from (and concurrently with) the other CPU instructions. For multiplication, the high- and low-order halves of the 64-bit product is written to HI and LO (respectively). For division, the quotient is written to LO and the remainder to HI. To access the results, a pair of instructions (Move from HI and Move from LO) is provided to copy

2006-736: A remark distinguishing libre (freedom) software from gratis (zero price) software, the Free Software Foundation says: "Free software is a matter of liberty, not price. To understand the concept, you should think of 'free' as in ' free speech ', not as in 'free beer ' ". ( See Gratis versus libre . ) In the late 1990s, other groups published their own definitions that describe an almost identical set of software. The most notable are Debian Free Software Guidelines published in 1997, and The Open Source Definition , published in 1998. The BSD -based operating systems, such as FreeBSD , OpenBSD , and NetBSD , do not have their own formal definitions of free software. Users of these systems generally find

2124-571: A significant part in the development of the Internet, the World Wide Web and the infrastructure of dot-com companies . Free software allows users to cooperate in enhancing and refining the programs they use; free software is a pure public good rather than a private good . Companies that contribute to free software increase commercial innovation . "We migrated key functions from Windows to Linux because we needed an operating system that

2242-498: A small set of licenses. The most popular of these licenses are: The Free Software Foundation and the Open Source Initiative both publish lists of licenses that they find to comply with their own definitions of free software and open-source software respectively: The FSF list is not prescriptive: free-software licenses can exist that the FSF has not heard about, or considered important enough to write about. So it

2360-410: Is a 64-bit version of the original shift instructions, used to specify constant shift distances of 0–31 bits. The second version is similar to the first, but adds 32 10 the shift amount field's value so that constant shift distances of 32–63 bits can be specified. The third version obtains the shift distance from the six low-order bits of a GPR. MIPS III added a supervisor privilege level in between

2478-516: Is a family of reduced instruction set computer (RISC) instruction set architectures (ISA) developed by MIPS Computer Systems, now MIPS Technologies , based in the United States . There are multiple versions of MIPS, including MIPS I, II, III, IV, and V, as well as five releases of MIPS32/64 (for 32- and 64-bit implementations, respectively). The early MIPS architectures were 32-bit; 64-bit versions were developed later. As of April 2017,

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2596-401: Is a matter of liberty , not price; all users are legally free to do what they want with their copies of a free software (including profiting from them) regardless of how much is paid to obtain the program. Computer programs are deemed "free" if they give end-users (not just the developer) ultimate control over the software and, subsequently, over their devices. The right to study and modify

2714-416: Is a memory penalty per allocation). Thus, few developers run their code under Memcheck (or any other Valgrind tool) all the time. They most commonly use such tools either to trace down some specific bug, or to verify that there are no latent bugs (of the kind Memcheck can detect) in the code. In addition to Memcheck, Valgrind has several other tools: exp-sgcheck (named exp-ptrcheck prior to version 3.7),

2832-536: Is also in the public domain, or otherwise available without restrictions. Proprietary software uses restrictive software licences or EULAs and usually does not provide users with the source code. Users are thus legally or technically prevented from changing the software, and this results in reliance on the publisher to provide updates, help, and support. ( See also vendor lock-in and abandonware ). Users often may not reverse engineer , modify, or redistribute proprietary software. Beyond copyright law, contracts and

2950-617: Is an example of a federally funded free-software project. Proprietary software, on the other hand, tends to use a different business model, where a customer of the proprietary application pays a fee for a license to legally access and use it. This license may grant the customer the ability to configure some or no parts of the software themselves. Often some level of support is included in the purchase of proprietary software, but additional support services (especially for enterprise applications) are usually available for an additional fee. Some proprietary software vendors will also customize software for

3068-466: Is biased by counting more vulnerabilities for the free software systems, since their source code is accessible and their community is more forthcoming about what problems exist as a part of full disclosure , and proprietary software systems can have undisclosed societal drawbacks, such as disenfranchising less fortunate would-be users of free programs. As users can analyse and trace the source code, many more people with no commercial constraints can inspect

3186-451: Is debate over the security of free software in comparison to proprietary software, with a major issue being security through obscurity . A popular quantitative test in computer security is to use relative counting of known unpatched security flaws. Generally, users of this method advise avoiding products that lack fixes for known security flaws, at least until a fix is available. Free software advocates strongly believe that this methodology

3304-539: Is denoted by the .d suffix. MIPS II removed the load delay slot and added several sets of instructions. For shared-memory multiprocessing, the Synchronize Shared Memory , Load Linked Word , and Store Conditional Word instructions were added. A set of Trap-on-Condition instructions were added. These instructions caused an exception if the evaluated condition is true. All existing branch instructions were given branch-likely versions that executed

3422-438: Is implementation-defined), to exceed or meet IEEE 754 accuracy requirements (respectively). The FP reciprocal and reciprocal square-root instructions do not comply with IEEE 754 accuracy requirements, and produce results that differ from the required accuracy by one or two units of last place (it is implementation defined). These instructions serve applications where instruction latency is more important than accuracy. MIPS V added

3540-454: Is making the transition to RISC-V . The first version of the MIPS architecture was designed by MIPS Computer Systems for its R2000 microprocessor, the first MIPS implementation. Both MIPS and the R2000 were introduced together in 1985. When MIPS II was introduced, MIPS was renamed MIPS I to distinguish it from the new version. MIPS Computer Systems ' R6000 microprocessor (1989)

3658-495: Is not endorsed by the FSF and does not use Linux-libre, it is also a popular distribution available without kernel blobs by default since 2011. The Linux community uses the term "blob" to refer to all nonfree firmware in a kernel whereas OpenBSD uses the term to refer to device drivers. The FSF does not consider OpenBSD to be blob free under the Linux community's definition of blob. Selling software under any free-software licence

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3776-601: Is not in the IT sector choose free software for their Internet information and sales sites, due to the lower initial capital investment and ability to freely customize the application packages. Most companies in the software business include free software in their commercial products if the licenses allow that. Free software is generally available at no cost and can result in permanently lower TCO ( total cost of ownership ) compared to proprietary software . With free software, businesses can fit software to their specific needs by changing

3894-472: Is only defined for 32-bit MIPS, but GCC has created a 64-bit variation called O64. For 64-bit, the N64 ABI by Silicon Graphics is most commonly used. The most important improvement is that eight registers are now available for argument passing; it also increases the number of floating-point registers to 32. There is also an ILP32 version called N32, which uses 32-bit pointers for smaller code, analogous to

4012-415: Is permissible, as is commercial use. This is true for licenses with or without copyleft . Since free software may be freely redistributed, it is generally available at little or no fee. Free software business models are usually based on adding value such as customization, accompanying hardware, support, training, integration, or certification. Exceptions exist however, where the user is charged to obtain

4130-521: Is possible for a license to be free and not in the FSF list. The OSI list only lists licenses that have been submitted, considered and approved. All open-source licenses must meet the Open Source Definition in order to be officially recognized as open source software. Free software, on the other hand, is a more informal classification that does not rely on official recognition. Nevertheless, software licensed under licenses that do not meet

4248-613: Is summarized at the Debian web site. It is rare that a license announced as being in-compliance with the FSF guidelines does not also meet the Open Source Definition , although the reverse is not necessarily true (for example, the NASA Open Source Agreement is an OSI-approved license, but non-free according to FSF). There are different categories of free software. Proponents of permissive and copyleft licenses disagree on whether software freedom should be viewed as

4366-474: Is support for Linux on MIPS64 little and big endian, for MIPS DSP ASE on MIPS32 , for s390x Decimal Floating Point instructions, for POWER8 ( Power ISA 2.07 ) instructions, for Intel AVX2 instructions, for Intel Transactional Synchronization Extensions, both RTM and HLE and initial support for Hardware Transactional Memory on POWER. The name Valgrind is a reference to the main entrance of Valhalla from Norse mythology . During development (before release)

4484-428: Is supported: base + displacement. Since MIPS I is a 32-bit architecture, loading quantities fewer than 32 bits requires the datum to be either sign-extended or zero-extended to 32 bits. The load instructions suffixed by "unsigned" perform zero extension; otherwise sign extension is performed. Load instructions source the base from the contents of a GPR (rs) and write the result to another GPR (rt). Store instructions source

4602-642: Is the link register . For integer multiplication and division instructions, which run asynchronously from other instructions, a pair of 32-bit registers, HI and LO , are provided. There is a small set of instructions for copying data between the general-purpose registers and the HI/LO registers. The program counter has 32 bits. The two low-order bits always contain zero since MIPS I instructions are 32 bits long and are aligned to their natural word boundaries. Instructions are divided into three types: R (register), I (immediate), and J (jump). Every instruction starts with

4720-683: Is the System Control Coprocessor (an essential part of the processor that is implementation-defined in MIPS I–V), CP1 is an optional floating-point unit (FPU) and CP2/3 are optional implementation-defined coprocessors (MIPS III removed CP3 and reused its opcodes for other purposes). For example, in the PlayStation video game console, CP2 is the Geometry Transformation Engine (GTE), which accelerates

4838-521: Is used by a number of Linux-based projects. In addition to the performance penalty, an important limitation of Memcheck is its inability to detect all cases of bounds errors in the use of static or stack-allocated data. The following code will pass the Memcheck tool in Valgrind without incident, despite containing the errors described in the comments: The inability to detect all errors involving

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4956-756: The Apache web server; and the Sendmail mail transport agent. Other influential examples include the Emacs text editor; the GIMP raster drawing and image editor; the X Window System graphical-display system; the LibreOffice office suite; and the TeX and LaTeX typesetting systems. From the 1950s up until the early 1970s, it was normal for computer users to have the software freedoms associated with free software, which

5074-830: The GNU operating system began in January 1984, and the Free Software Foundation (FSF) was founded in October 1985. He developed a free software definition and the concept of " copyleft ", designed to ensure software freedom for all. Some non-software industries are beginning to use techniques similar to those used in free software development for their research and development process; scientists, for example, are looking towards more open development processes, and hardware such as microchips are beginning to be developed with specifications released under copyleft licenses ( see

5192-744: The Linux kernel and other device drivers motivated some developers in Ireland to launch gNewSense , a Linux-based distribution with all the binary blobs removed. The project received support from the Free Software Foundation and stimulated the creation, headed by the Free Software Foundation Latin America , of the Linux-libre kernel. As of October 2012 , Trisquel is the most popular FSF endorsed Linux distribution ranked by Distrowatch (over 12 months). While Debian

5310-661: The OpenCores project, for instance ). Creative Commons and the free-culture movement have also been largely influenced by the free software movement. In 1983, Richard Stallman , longtime member of the hacker community at the MIT Artificial Intelligence Laboratory , announced the GNU Project, saying that he had become frustrated with the effects of the change in culture of the computer industry and its users. Software development for

5428-410: The source code was distributed to use these programs. Software was also shared and distributed as printed source code ( Type-in program ) in computer magazines (like Creative Computing , SoftSide , Compute! , Byte , etc.) and books, like the bestseller BASIC Computer Games . By the early 1970s, the picture changed: software costs were dramatically increasing, a growing software industry

5546-554: The x32 ABI . Both run under the 64-bit mode of the CPU. The N32 and N64 ABIs pass the first eight arguments to a function in the registers $ a0 - $ a7 ; subsequent arguments are passed on the stack. The return value (or a pointer to it) is stored in the registers $ v0 ; a second return value may be stored in $ v1 . In both the N32 and N64 ABIs all registers are considered to be 64-bits wide. A few attempts have been made to replace O32 with

5664-408: The 32-bit sign-extended result to the sum of the program counter (instruction address) and 8 10 . Jumps have two versions: absolute and register-indirect. Absolute jumps ("Jump" and "Jump and Link") compute the address to which control is transferred by shifting the 26-bit instr_index left by two bits and concatenating the 28-bit result with the four high-order bits of the address of the instruction in

5782-399: The A bits set to "invalid"). This feature enables Memcheck to detect off-by-one errors where a program reads or writes outside an allocated block by a small amount. The problems Memcheck can detect and warn about include the following: The price of this is lost performance. Programs running under Memcheck usually run 20–30 times slower than running outside Valgrind and use more memory (there

5900-449: The CPU and FPU convert single- and double-precision floating-point numbers into doubleword integers and vice versa. MIPS IV is the fourth version of the architecture. It is a superset of MIPS III and is compatible with all existing versions of MIPS. MIPS IV was designed to mainly improve floating-point (FP) performance. To improve access to operands, an indexed addressing mode (base + index, both sourced from GPRs) for FP loads and stores

6018-557: The Free Software Definition cannot rightly be considered free software. Apart from these two organizations, the Debian project is seen by some to provide useful advice on whether particular licenses comply with their Debian Free Software Guidelines . Debian does not publish a list of approved licenses, so its judgments have to be tracked by checking what software they have allowed into their software archives. That

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6136-426: The Free Software Foundation recommends using the term "free software" rather than " open-source software " (an alternative, yet similar, concept coined in 1998), because the goals and messaging are quite dissimilar. According to the Free Software Foundation, "Open source" and its associated campaign mostly focus on the technicalities of the public development model and marketing free software to businesses, while taking

6254-631: The GNU operating system began in January 1984, and the Free Software Foundation (FSF) was founded in October 1985. An article outlining the project and its goals was published in March 1985 titled the GNU Manifesto . The manifesto included significant explanation of the GNU philosophy, Free Software Definition and " copyleft " ideas. The Linux kernel , started by Linus Torvalds , was released as freely modifiable source code in 1991. The first licence

6372-533: The GPRs and HI/LO registers. For shared-memory multiprocessing, the Load Linked Double Word , and Store Conditional Double Word instructions were added. Existing instructions originally defined to operate on 32-bit words were redefined, where necessary, to sign-extend the 32-bit results to permit words and doublewords to be treated identically by most instructions. Among those instructions redefined

6490-525: The Internet. Users can easily download and install those applications via a package manager that comes included with most Linux distributions . The Free Software Directory maintains a large database of free-software packages. Some of the best-known examples include Linux-libre , Linux-based operating systems, the GNU Compiler Collection and C library ; the MySQL relational database;

6608-509: The MIPS architecture has ceased. The company has joined the RISC-V foundation and future processor designs will be based on the RISC-V architecture. In spite of this, some licensees such as Loongson continue with new extension of MIPS-compatible ISAs on their own. In January 2024, Loongson won a case over rights to use MIPS architecture. MIPS is a modular architecture supporting up to four coprocessors (CP0/1/2/3). In MIPS terminology, CP0

6726-502: The MIPS16e ASE. A disadvantage of MIPS16e is that it requires a mode switch before any of its 16-bit instructions can be processed. microMIPS adds versions of the most-frequently used 32-bit instructions that are encoded as 16-bit instructions. This allows programs to intermix 16- and 32-bit instructions without having to switch modes. microMIPS was introduced alongside of MIPS32/64 Release 3, and each subsequent release of MIPS32/64 has

6844-519: The MIPS32 and MIPS64 specifications, as were cache control instructions . For the purpose of cache control, both SYNC and SYNCI instructions were prepared. MIPS32/MIPS64 Release 6 in 2014 added the following: Removed infrequently used instructions: Reorganized the instruction encoding, freeing space for future expansions. The microMIPS32/64 architectures are supersets of the MIPS32 and MIPS64 architectures (respectively) designed to replace

6962-584: The Or Immediate instruction to load a 32-bit immediate into a register. MIPS I has instructions to perform left and right logical shifts and right arithmetic shifts. The operand is obtained from a GPR (rt), and the result is written to another GPR (rd). The shift distance is obtained from either a GPR (rs) or a 5-bit "shift amount" (the "sa" field). MIPS I has instructions for signed and unsigned integer multiplication and division. These instructions source their operands from two GPRs and write their results to

7080-501: The Quantum Effect Devices R5000 (1996) and RM7000 (1998). The R10000, fabricated and sold by NEC Electronics and Toshiba, and its derivatives were used by NEC, Pyramid Technology, Silicon Graphics, and Tandem Computers (among others) in workstations, servers, and supercomputers. The R5000 and R7000 found use in high-end embedded systems, personal computers, and low-end workstations and servers. A derivative of

7198-816: The R5000 from Toshiba, the R5900, was used in Sony Computer Entertainment's Emotion Engine , which powered its PlayStation 2 game console. Announced on October 21, 1996, at the Microprocessor Forum 1996 alongside the MIPS Digital Media Extensions (MDMX) extension, MIPS V was designed to improve the performance of 3D graphics transformations. In the mid-1990s, a major use of non-embedded MIPS microprocessors were graphics workstations from Silicon Graphics. MIPS V

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7316-482: The access of stack allocated data is especially noteworthy since certain types of stack errors make software vulnerable to the classic stack smashing exploit . Free software Free software , libre software , libreware sometimes known as freedom-respecting software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute it and any adapted versions. Free software

7434-478: The base from the contents of a GPR (rs) and the store data from another GPR (rt). All load and store instructions compute the memory address by summing the base with the sign-extended 16-bit immediate. MIPS I requires all memory accesses to be aligned to their natural word boundaries, otherwise an exception is signaled. To support efficient unaligned memory accesses, there are load/store word instructions suffixed by "left" or "right". All load instructions are followed by

7552-477: The branch delay slot. Register-indirect jumps transfer control to the instruction at the address sourced from a GPR (rs). The address sourced from the GPR must be word-aligned, else an exception is signaled after the instruction in the branch delay slot is executed. Branch and jump instructions that link (except for "Jump and Link Register") save the return address to GPR 31. The "Jump and Link Register" instruction permits

7670-409: The callee needs to save its arguments, but the registers are not stored there by the caller. The return value is stored in register $ v0 ; a second return value may be stored in $ v1 . The ABI took shape in 1990 and was last updated in 1994. This perceived slowness, along with an antique floating-point model with only 16 registers, has encouraged the proliferation of many other calling conventions. It

7788-588: The code and find bugs and loopholes than a corporation would find practicable. According to Richard Stallman, user access to the source code makes deploying free software with undesirable hidden spyware functionality far more difficult than for proprietary software. Some quantitative studies have been done on the subject. In 2006, OpenBSD started the first campaign against the use of binary blobs in kernels . Blobs are usually freely distributable device drivers for hardware from vendors that do not reveal driver source code to users or developers. This restricts

7906-530: The contents of HI or LO to a GPR. These instructions are interlocked: reads of HI and LO do not proceed past an unfinished arithmetic instruction that will write to HI and LO. Another pair of instructions (Move to HI or Move to LO) copies the contents of a GPR to HI and LO. These instructions are used to restore HI and LO to their original state after exception handling. Instructions that read HI or LO must be separated by two instructions that do not write to HI or LO. All MIPS I control flow instructions are followed by

8024-496: The current version of MIPS is MIPS32/64 Release 6. MIPS32/64 primarily differs from MIPS I–V by defining the privileged kernel mode System Control Coprocessor in addition to the user mode architecture. The MIPS architecture has several optional extensions: MIPS-3D , a simple set of floating-point SIMD instructions dedicated to common 3D tasks; MDMX (MaDMaX), a more extensive integer SIMD instruction set using 64-bit floating-point registers; MIPS16e, which adds compression to

8142-557: The dominant personal computing platform. ARC found little success in personal computers, but the R4000 (and the R4400 derivative) were widely used in workstation and server computers, especially by its largest user, Silicon Graphics . Other uses of the R4000 included high-end embedded systems and supercomputers. MIPS III was eventually implemented by a number of embedded microprocessors. Quantum Effect Design 's R4600 (1993) and its derivatives

8260-415: The efficiency and performance of certain workloads, such as digital signal processing . MIPS has had several calling conventions, especially on the 32-bit platform. The O32 ABI is the most commonly-used ABI, owing to its status as the original System V ABI for MIPS. It is strictly stack-based, with only four registers $ a0 - $ a3 available to pass arguments. Space on the stack is reserved in case

8378-492: The ethical issue of user rights very lightly or even antagonistically. Stallman has also stated that considering the practical advantages of free software is like considering the practical advantages of not being handcuffed, in that it is not necessary for an individual to consider practical reasons in order to realize that being handcuffed is undesirable in itself. The FSF also notes that "Open Source" has exactly one specific meaning in common English, namely that "you can look at

8496-411: The exception handler. MIPS has 32 floating-point registers. Two registers are paired for double precision numbers. Odd numbered registers cannot be used for arithmetic or branching, just as part of a double precision register pair, resulting in 16 usable registers for most instructions (moves/copies and loads/stores were not affected). Single precision is denoted by the .s suffix, while double precision

8614-505: The existing kernel and user privilege levels. This feature only affected the implementation-defined System Control Processor (Coprocessor 0). MIPS III removed the Coprocessor 3 (CP3) support instructions, and reused its opcodes for the new doubleword instructions. The remaining coprocessors gained instructions to move doublewords between coprocessor registers and the GPRs. The floating general registers (FGRs) were extended to 64 bits and

8732-480: The floating point coprocessor also had several instructions added to it. An IEEE 754-compliant floating-point square root instruction was added. It supported both single- and double-precision operands. A set of instructions that converted single- and double-precision floating-point numbers to 32-bit words were added. These complemented the existing conversion instructions by allowing the IEEE rounding mode to be specified by

8850-409: The government charged that bundled software was anti-competitive . While some software might always be free, there would henceforth be a growing amount of software produced primarily for sale. In the 1970s and early 1980s, the software industry began using technical measures (such as only distributing binary copies of computer programs ) to prevent computer users from being able to study or adapt

8968-545: The host processor . Instead, Valgrind first translates the program into a temporary, simpler form called intermediate representation (IR), which is a processor-neutral, static single assignment form -based form. After the conversion, a tool (see below) is free to do whatever transformations it would like on the IR, before Valgrind translates the IR back into machine code and lets the host processor run it. Valgrind recompiles binary code to run on host and target (or simulated) CPUs of

9086-402: The instruction in the branch delay slot only if the branch is taken. These instructions improve performance in certain cases by allowing useful instructions to fill the branch delay slot. Doubleword load and store instructions for COP1–3 were added. Consistent with other memory access instructions, these loads and stores required the doubleword to be naturally aligned. The instruction set for

9204-632: The instruction instead of the Floating Point Control and Status Register. MIPS III is a backwards-compatible extension of MIPS II that added support for 64-bit memory addressing and integer operations. The 64-bit data type is called a doubleword, and MIPS III extended the general-purpose registers, HI/LO registers, and program counter to 64 bits to support it. New instructions were added to load and store doublewords, to perform integer addition, subtraction, multiplication, division, and shift operations on them, and to move doubleword between

9322-403: The instruction stream to reduce the space programs take up; and MIPS MT, which adds multithreading capability. Computer architecture courses in universities and technical schools often study the MIPS architecture. The architecture greatly influenced later RISC architectures such as Alpha . In March 2021, MIPS announced that the development of the MIPS architecture had ended as the company

9440-421: The list, but later added first in the list as it was considered very important. Freedoms 1 and 3 require source code to be available because studying and modifying software without its source code can range from highly impractical to nearly impossible. Thus, free software means that computer users have the freedom to cooperate with whom they choose, and to control the software they use. To summarize this into

9558-474: The memory address in question points to an allocated, non-freed memory block), stored in the so-called V bits and A bits respectively. As data is moved around or manipulated, the instrumentation code keeps track of the A and V bits, so they are always correct on a single-bit level. In addition, Memcheck replaces the standard C++ allocators and C memory allocator with its own implementation, which also includes memory guards around all allocated blocks (with

9676-616: The mid-1990s. The first MIPS IV implementation was the MIPS Technologies R8000 microprocessor chipset (1994). The design of the R8000 began at Silicon Graphics, Inc. and it was only used in high-end workstations and servers for scientific and technical applications where high performance on large floating-point workloads was important. Later implementations were the MIPS Technologies R10000 (1996) and

9794-412: The most recent versions of both the 32-bit and 64-bit designs making them available without any licensing or royalty fees as well as granting participants licenses to existing MIPS patents. In March 2019, one version of the architecture was made available under a royalty-free license, but later that year the program was shut down again. In March 2021, Wave Computing announced that the development of

9912-398: The processing of geometry in 3D computer graphics. MIPS is a load/store architecture (also known as a register-register architecture ); except for the load/store instructions used to access memory , all instructions operate on the registers. MIPS I has thirty-two 32-bit general-purpose registers (GPR). Register $ 0 is hardwired to zero and writes to it are discarded. Register $ 31

10030-482: The project was named Heimdall ; however, the name would have conflicted with a security package. The original author of Valgrind is Julian Seward , who in 2006 won a Google-O'Reilly Open Source Award for his work on Valgrind. Several others have also made significant contributions, including Nicholas Nethercote, Bart Van Assche, Florian Krohm, Tom Hughes, Philippe Waroquiers, Mark Wielaard, Paul Floyd, Petar Jovanovic, Carl Love, Cerion Armour-Brown and Ivo Raisr. It

10148-507: The requirement for instructions to use even-numbered register only was removed. This is incompatible with earlier versions of the architecture; a bit in the floating-point control/status register is used to operate the MIPS III floating-point unit (FPU) in a MIPS I- and II-compatible mode. The floating-point control registers were not extended for compatibility. The only new floating-point instructions added were those to copy doublewords between

10266-562: The result to a third GPR (rd). Alternatively, addition can source one of the operands from a 16-bit immediate (which is sign-extended to 32 bits). The instructions for addition and subtraction have two variants: by default, an exception is signaled if the result overflows; instructions with the "unsigned" suffix do not signal an exception. The overflow check interprets the result as a 32-bit two's complement integer. MIPS I has instructions to perform bitwise logical AND, OR, XOR, and NOR. These instructions source their operands from two GPRs and write

10384-413: The result to a third GPR. By default, the operands are interpreted as signed integers. The variants of these instructions that are suffixed with "unsigned" interpret the operands as unsigned integers (even those that source an operand from the sign-extended 16-bit immediate). The Load Immediate Upper instruction copies the 16-bit immediate into the high-order 16 bits of a GPR. It is used in conjunction with

10502-427: The result to a third GPR. The AND, OR, and XOR instructions can alternatively source one of the operands from a 16-bit immediate (which is zero-extended to 32 bits). The Set on relation instructions write one or zero to the destination register if the specified relation is true or false. These instructions source their operands from two GPRs or one GPR and a 16-bit immediate (which is sign-extended to 32 bits), and write

10620-410: The return address to be saved to any writable GPR. MIPS I has two instructions for software to signal an exception: System Call and Breakpoint. System Call is used by user mode software to make kernel calls; and Breakpoint is used to transfer control to a debugger via the kernel's exception handler. Both instructions have a 20-bit Code field that can contain operating environment-specific information for

10738-471: The same architecture. It also includes a GDB stub to allow debugging of the target program as it runs in Valgrind, with "monitor commands" that allow querying the Valgrind tool for various information. A considerable amount of performance is lost in these transformations (and usually, the code the tool inserts); usually, code run with Valgrind and the "none" tool (which does nothing to the IR) runs at 20% to 25% of

10856-511: The same set of software to be acceptable, but sometimes see copyleft as restrictive. They generally advocate permissive free software licenses , which allow others to use the software as they wish, without being legally forced to provide the source code. Their view is that this permissive approach is more free. The Kerberos , X11 , and Apache software licenses are substantially similar in intent and implementation. There are thousands of free applications and many operating systems available on

10974-435: The shift in climate surrounding the computer world and its users. In his initial declaration of the project and its purpose, he specifically cited as a motivation his opposition to being asked to agree to non-disclosure agreements and restrictive licenses which prohibited the free sharing of potentially profitable in-development software, a prohibition directly contrary to the traditional hacker ethic . Software development for

11092-461: The software applications as they saw fit. In 1980, copyright law was extended to computer programs. In 1983, Richard Stallman , one of the original authors of the popular Emacs program and a longtime member of the hacker community at the MIT Artificial Intelligence Laboratory , announced the GNU Project , the purpose of which was to produce a completely non-proprietary Unix-compatible operating system, saying that he had become frustrated with

11210-443: The software themselves or by hiring programmers to modify it for them. Free software often has no warranty, and more importantly, generally does not assign legal liability to anyone. However, warranties are permitted between any two parties upon the condition of the software and its usage. Such an agreement is made separately from the free software license. A report by Standish Group estimates that adoption of free software has caused

11328-411: The source and use the same license. This requirement does not extend to other software from the same developer. The claim of incompatibility between commercial companies and free software is also a misunderstanding. There are several large companies, e.g. Red Hat and IBM (IBM acquired RedHat in 2019), which do substantial commercial business in the development of free software. Free software played

11446-529: The source code." It states that while the term "Free Software" can lead to two different interpretations, at least one of them is consistent with the intended meaning unlike the term "Open Source". The loan adjective " libre " is often used to avoid the ambiguity of the word "free" in the English language , and the ambiguity with the older usage of "free software" as public-domain software. ( See Gratis versus libre . ) The first formal definition of free software

11564-441: The speed of the normal program. There are multiple tools included with Valgrind (and several external ones). The default (and most used) tool is Memcheck . Memcheck inserts extra instrumentation code around almost all instructions, which keeps track of the validity (all unallocated memory starts as invalid or "undefined", until it is initialized into a deterministic state, possibly from other memory) and addressability (whether

11682-401: The spirit of cooperation once prevalent among hackers during the early days of computing. Free software differs from: For software under the purview of copyright to be free, it must carry a software license whereby the author grants users the aforementioned rights. Software that is not covered by copyright law, such as software in the public domain , is free as long as the source code

11800-747: The total to eight. FP comparison and branch instructions were redefined so they could specify which condition bit was written or read (respectively); and the delay slot in between an FP branch that read the condition bit written to by a prior FP comparison was removed. Support for partial predication was added in the form of conditional move instructions for both GPRs and FPRs; and an implementation could choose between having precise or imprecise exceptions for IEEE 754 traps. MIPS IV added several new FP arithmetic instructions for both single- and double-precision FPNs: fused-multiply add or subtract, reciprocal, and reciprocal square-root. The FP fused-multiply add or subtract instructions perform either one or two roundings (it

11918-495: The users' freedom effectively to modify the software and distribute modified versions. Also, since the blobs are undocumented and may have bugs , they pose a security risk to any operating system whose kernel includes them. The proclaimed aim of the campaign against blobs is to collect hardware documentation that allows developers to write free software drivers for that hardware, ultimately enabling all free operating systems to become or remain blob-free. The issue of binary blobs in

12036-414: Was Load Word . In MIPS III it sign-extends words to 64 bits. To complement Load Word , a version that zero-extends was added. The R instruction format's inability to specify the full shift distance for 64-bit shifts (its 5-bit shift amount field is too narrow to specify the shift distance for doublewords) required MIPS III to provide three 64-bit versions of each MIPS I shift instruction. The first version

12154-676: Was a proprietary software licence. However, with version 0.12 in February 1992, he relicensed the project under the GNU General Public License . Much like Unix, Torvalds' kernel attracted the attention of volunteer programmers. FreeBSD and NetBSD (both derived from 386BSD ) were released as free software when the USL v. BSDi lawsuit was settled out of court in 1993. OpenBSD forked from NetBSD in 1995. Also in 1995, The Apache HTTP Server , commonly referred to as Apache,

12272-497: Was added in version 3.6.0. Support for Solaris was added in version 3.11.0. Support for OS X was added in version 3.5.0. Support for FreeBSD x86 and amd64 was added in version 3.18.0. Support for FreeBSD aarch64 was added in version 3.23.0. There are unofficial ports to other Unix-like platforms (like OpenBSD , NetBSD and QNX). From version 3.7.0 the ARM/ Android platform support was added. Since version 3.9.0 there

12390-411: Was added, as were prefetch instructions for performing memory prefetching and specifying cache hints (these supported both the base + offset and base + index addressing modes). MIPS IV added several features to improve instruction-level parallelism. To alleviate the bottleneck caused by a single condition bit, seven condition code bits were added to the floating-point control and status register, bringing

12508-538: Was announced on December 6, 2012. According to the Product Marketing Director at MIPS, Release 4 was skipped because the number four is perceived as unlucky in many Asian cultures. In December 2018, Wave Computing, the new owner of the MIPS architecture, announced that MIPS ISA would be open-sourced in a program dubbed the MIPS Open initiative. The program was intended to open up access to

12626-407: Was based on MIPS V and retains all of its features as an optional Coprocessor 1 (FPU) feature called Paired-Single. When MIPS Technologies was spun-out of Silicon Graphics in 1998, it refocused on the embedded market. Through MIPS V, each successive version was a strict superset of the previous version, but this property was found to be a problem, and the architecture definition was changed to define

12744-402: Was competing with the hardware manufacturer's bundled software products (free in that the cost was included in the hardware cost), leased machines required software support while providing no revenue for software, and some customers able to better meet their own needs did not want the costs of "free" software bundled with hardware product costs. In United States vs. IBM , filed January 17, 1969,

12862-600: Was completed by the integer-only MDMX extension to provide a complete system for improving the performance of 3D graphics applications. MIPS V implementations were never introduced. On May 12, 1997, Silicon Graphics announced the H1 ("Beast") and H2 ("Capitan") microprocessors. The former was to have been the first MIPS V implementation, and was due to be introduced in the first half of 1999. The H1 and H2 projects were later combined and eventually canceled in 1998. While there have not been any MIPS V implementations, MIPS64 Release 1 (1999)

12980-511: Was introduced in 1999. MIPS Computer Systems ' R4000 microprocessor (1991) was the first MIPS III implementation. It was designed for use in personal, workstation, and server computers. MIPS Computer Systems aggressively promoted the MIPS architecture and R4000, establishing the Advanced Computing Environment (ACE) consortium to advance its Advanced RISC Computing (ARC) standard, which aimed to establish MIPS as

13098-419: Was published by FSF in February 1986. That definition, written by Richard Stallman , is still maintained today and states that software is free software if people who receive a copy of the software have the following four freedoms. The numbering begins with zero, not only as a spoof on the common usage of zero-based numbering in programming languages, but also because "Freedom 0" was not initially included in

13216-476: Was released under the Apache License 1.0 . All free-software licenses must grant users all the freedoms discussed above. However, unless the applications' licenses are compatible, combining programs by mixing source code or directly linking binaries is problematic, because of license technicalities . Programs indirectly connected together may avoid this problem. The majority of free software falls under

13334-425: Was removed in version 3.16.0. It was an experimental tool to find stack and global array overrun errors, which Memcheck cannot find. There are also several externally developed tools available. One such tool is ThreadSanitizer, another detector of race conditions . As of version 3.4.0, Valgrind supports Linux on x86 , x86-64 and PowerPC . Support for Linux on ARMv7 (used for example in certain smartphones )

13452-679: Was stable and reliable – one that would give us in-house control. So if we needed to patch, adjust, or adapt, we could." Official statement of the United Space Alliance , which manages the computer systems for the International Space Station (ISS), regarding their May 2013 decision to migrate ISS computer systems from Windows to Linux The economic viability of free software has been recognized by large corporations such as IBM , Red Hat , and Sun Microsystems . Many companies whose core business

13570-453: Was the first MIPS II implementation. Designed for servers, the R6000 was fabricated and sold by Bipolar Integrated Technology , but was a commercial failure. During the mid-1990s, many new 32-bit MIPS processors for embedded systems were MIPS II implementations because the introduction of the 64-bit MIPS III architecture in 1991 left MIPS II as the newest 32-bit MIPS architecture until MIPS32

13688-437: Was the first instruction set to exploit floating-point SIMD with existing resources. The first release of MIPS32, based on MIPS II, added conditional moves, prefetch instructions , and other features from the R4000 and R5000 families of 64-bit processors. The first release of MIPS64 adds a MIPS32 mode to run 32-bit code. The MUL and MADD ( multiply-add ) instructions, previously available in some implementations, were added to

13806-407: Was typically public-domain software . Software was commonly shared by individuals who used computers and by hardware manufacturers who welcomed the fact that people were making software that made their hardware useful. Organizations of users and suppliers, for example, SHARE , were formed to facilitate exchange of software. As software was often written in an interpreted language such as BASIC ,

13924-513: Was widely used in high-end embedded systems and low-end workstations and servers. MIPS Technologies' R4200 (1994), was designed for embedded systems, laptop, and personal computers. A derivative, the R4300i, fabricated by NEC Electronics , was used in the Nintendo 64 game console. The Nintendo 64, along with the PlayStation , were among the highest volume users of MIPS architecture processors in

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